To a solution of compound 10 (3.00 g, 11.6 mmol) in CH2Cl2 at 0° C. (60 mL) was added piperazine-1-ethanol (11) (1.82 g, 14.0 mmol), EDC (3.12 g, 16.3 mmol), HOBt (0.20 g) and DIPEA (5.8 mL, 34.9 mmol). The mixture was allowed to warm to RT over 16 h. TLC (5% MeOH/CH2Cl2) showed no starting material. The reaction mixture was diluted with CH2Cl2 (50 mL), washed with water (2×40 mL) and dried. Evaporation of organic layer gave a residue. The residue was triturated with diisopropyl ether (20 mL) to get 3-[4-(2-hydroxy-ethyl)-piperazine-1-carbonyl]-7-oxa-bicyclo[2.2.1]heptane-2-carboxylic acid benzyl ester (12) as a white solid. Yield: 3.24 g (72%). Mp 72-75 C. 1H NMR (300 MHz, CDCl3) δ 1.42-1.56 (m, 2H); 1.76-1.82 (m, 2H); 2.02 (s, 2H); 2.29-2.51 (m, 4H); 2.90 (d, J=6.4 Hz, 1H); 3.08 (d, J=6.4 Hz, 1H); 3.18-3.24 (m, 2H); 3.41 (bs, 1H); 3.60 (t, J=2.3 Hz, 2H); 3.69 (bs, 1H); 4.90 (dd, J=6.8 Hz, 2.3 Hz, 2H); 5.08 (s, 2H); 7.28-7.40 (m, 5H).
